Car radios--and this term will be used although the radios may include, typically, cassette recorders and other electronic accessory equipment--installed in automobiles have a high value with respect to their weight and size and, consequently, are subject to theft. Car radios frequently are stolen from parked cars; breaking into a car is a simple matter for a professional thief, and, since the car radios are small, they can be stolen and easily hidden.
It has previously been proposed to reduce such thefts by providing for mechanical locks for the car radios to prevent their unauthorized removal without a key, by coupling car radios to otherwise already present automotive alarm systems so that removal of the car radio will trigger an alarm; the effectiveness of all such arrangements, however, is limited.